Melon field soil gets 'warm shower' for disinfection
By Guan Wenfei and Hu Xiaocen |
August 28, 2012, Tuesday
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Print Edition
Print Edition
DOZENS of hoses with small holes are rolled out in the cantaloupe field in Jiading District, through which warm water is pumped into the soil - the soil is getting a "warm shower" to kill the bacteria and dilute the salt.
Gu Haifeng, an expert from the cantaloupe research center at Huating Town, said it's inevitable that the soil has bacteria and salt. The plants secrete toxins from the roots, which will affect the growth of the fruit in the following growing season. This is known as the "continuous cropping obstacle." So the farmers have to disinfect the soil between the two melon growing seasons, which is usually done in summer.
The staff of the research center first thought about exposing the soil to the sun as most bacteria can be killed by sunlight. They turned the soil over to expose the bacteria beneath. But this method only killed bacteria in the soil up to 15 centimeters deep and it didn't desalinize the soil.
Later they tried pouring water in the greenhouse, which penetrated the soil up to 40 centimeters, and had the sun heat up the water. But the temperature wasn't high enough. The disinfection effect is discounted if the temperature doesn't rise above 50 degrees Celsius.
The center then tried disinfectants. The available products either had little effect or polluted the environment. And the cost was too much a burden for the farmers to bear.
Taking all the given methods into consideration, warm water disinfection seemed to surpass the rest. Using water above 60 degrees to water the field can kill bacteria 30 to 40 centimeters deep and wash away the salt. But the effect of this method will not be known until the coming autumn when farmers can check the quality of the melons, Gu said.
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